Field of the Invention
Exemplary embodiments of the present invention relate to a drilling worktable for manufacturing tube support plates and a method of manufacturing tube support plates using the same, and more particularly, to a drilling worktable for manufacturing tube support plates of a steam generator, which constitutes a primary system of a nuclear power plant, by drilling members to be processed, and a method of manufacturing tube support plates using the same.
Description of the Related Art
A nuclear power plant is largely divided into a primary system and a secondary system. The primary system includes steam generation-related devices and an SG (Steam Generator) is a representative example thereof. Meanwhile, the secondary system includes electricity production-related devices and devices for restoring steam to water.
High-temperature primary coolant supplied from a reactor is introduced into an SG (Steam Generator) and exchanges heat with secondary coolant outside heat transfer tubes while flowing along the heat transfer tubes inside the steam generator. As a result, heat energy is transferred from the primary side to the secondary side.
The heat transfer tubes are fitted, in a bundle form, to a plurality of TSPS (Tube Support Plates) and heat transfer tube insertion holes formed on one TS (Tube Sheet), so as to be supported within the steam generator.
The TSPS (Tube Support Plates) are manufactured through a heat transfer tube insertion hole drilling step, a deburring step, a broaching step, a deburring step, a honing step, and an inspection step.
In this case, maintaining flatness of a member to be processed in the drilling step has a great influence on quality of the tube support plates which are finished products. This is particularly because the broaching step, which is a step subsequent to the drilling step, is a process sensitive to material flatness.
In this context, U.S. Patent Laid-Open Publication No. 2013-0259588 (Patent Document 1) is disclosed as the related art of a drilling worktable for manufacturing tube support plates used in the drilling step and a method of manufacturing tube support plates using the same. A conventional drilling support beam for manufacturing tube support plates is disclosed as another related art, and is shown in FIG. 10.
Referring to FIG. 10, conventional drilling support beams for manufacturing tube support plates 20 are located between a member to be processed 10 and a device worktable 30 and then used. The drilling support beams 20 each have a bar shape. The drilling support beams 20 are located at a lower surface of the member to be processed 10 to locally support a vertical load thereof.
In addition, the conventional drilling support beams for manufacturing tube support plates 20 do not uniformly support a whole load of the member to be processed 10 but locally support the load only at parts at which the drilling support beams 20 are located, when the drilling step is performed in a direction of the arrow X in FIG. 10. Accordingly, there is a problem in that the member to be processed 10 is entirely bent or twisted due to stress according to the drilling.
For this reason, there is a problem in that the member to be processed 10 is bent or twisted so that a heat transfer tube insertion hole is not drilled at an accurate position thereof or vertical straightness of the hole is lowered below a certain criteria. In addition, since flatness of the member to be processed 10 is further lowered in the broaching step which is a step subsequent to the drilling step, there is a problem in that a poor tube support plate which does not satisfy a certain criteria is produced to thereby cause unnecessary times and costs for manufacturing a new tube support plate again.
[Patent Document 1] U.S. Patent Laid-Open Publication No. 2013-0259588